DESCRIPTION: The respiratory muscles are a major determinant of thoracic cavity shape and thus the distribution of regional ventilation. Respiratory insufficiency is the usual cause of death in many primary neuromuscular disorders. Respiratory muscle fatigue is believed to be a major factor in hypercarbic respiratory failure associated with lung and/or cardiovascular diseases. A recent NHLBI workshop summarized the difficulty of studying respiratory muscle fatigue because of our limited understanding of the relationships between tension developed by the respiratory muscles and pressures which expand the thoracic cavity and other parameters which can be measured in intact animals or man. Much of the benefit of lung volume reduction surgery for end stage emphysema is proposed to be secondary to improved function of the respiratory muscles principally the diaphragm. This project utilizes a video roentgenographic technique to determine the regional shape, displacements and muscle shortening of the diaphragm and rib cage to elucidate the basic mechanics of the diaphragm and rib cage. By comparing muscle shortening and curvature of the diaphragm in intact animals under conditions in which the transdiaphragmatic pressure and muscle tension can be measured, the relationship between muscle tension and pressures can be determined. The detailed three dimensional anatomic data provided by this methodology coupled with more conventional physiologic measurements should answer important questions posed by previous studies of the coupling of the diaphragm abdomen and rib cage. The investigators will verify and extend two models of diaphragm structure and functions developed in the current period of the project. These models are consistent with data obtained in this project which contradict previous qualitative models. The models offer testable predictions about the mechanisms of failure of the diaphragm as an inspiratory muscle at high lung volumes. In the current proposal, the investigators will extend our knowledge and techniques developed in animals to study diaphragm and chest wall function in normal humans and patients with severe emphysema before and after lung volume reduction surgery.